A conventional pulse radar apparatus comprises a transmitting section configured to generate a pulsed transmission signal formed of a high-frequency carrier wave, a transmitting antenna configured to emit the transmission signal generated by the transmitting section to the air as radio wave, a receiving antenna configured to receive reflected wave of the radio wave emitted from the transmitting antenna and returned by being reflected by an object, a receiving section configured to down-convert the received signal received from the receiving antenna to a baseband signal, and a signal processing section configured to input the baseband signal from the receiving section to calculate a distance to the object and others. The signal processing section is provided with a control section configured to output control signals for controlling the transmitting and receiving sections.
Because the transmitting and receiving sections and the transmitting and receiving antennas among the components of the pulse radar described above process high-frequency transmitting and received signals, they are disposed on a high-frequency printed circuit board suitable for transmitting the high-frequency signals. In contrary to that, because the signal processing section processes the baseband signal down-converted by the receiving section and the control section provided in the signal processing section also outputs relatively low frequency control signals to the transmitting and receiving sections, they are normally disposed on a low-frequency printed circuit board.
As described above, the pulse radar uses at least two printed circuit boards of the high-frequency printed circuit board and the low-frequency printed circuit board. Then, a signal transmitting means for transmitting the signals between the respective printed circuit boards is required. Conventionally, an inexpensive and general-purpose multi-pin board-to-board connector is widely used as the signal transmitting means for transmitting the signals between printed circuit boards.
Lately, a need to mount a pulse radar in a vehicle is increasing in order to prevent collision of the vehicle and to support parking of the vehicle. Then, an in-vehicle pulse radar is used to detect information on an object existing in front of or around the vehicle. Because downsizing and cutting costs of a radar apparatus are strongly demanded for such in-vehicle pulse radar, printed circuit boards and a board-to-board connector for connecting the printed circuit boards used in the in-vehicle pulse radar are also required to downsize and to lower costs.
The downsized multi-pin board-to-board connector has a problem that it is liable to cause interferences due to electromagnetic coupling between terminals (pins) because a pitch between the terminals is narrow and high-frequency and broadband signals are transmitted more. If such interference between the terminals occurs, a control signal that propagates through a terminal leaks into a receiving signal propagating through another predetermined terminal as a noise signal. Then, it causes a problem that it is unable to detect the information on the object from the receiving signal if the noise signal leaks into the receiving signal in the multi-pin board-to-board connector as described above.
There have been known means for preventing the leak of the noise signal in the board-to-board connector as described above since the past. Patent Document 1 discloses that enhancing isolation of the board-to-board connector itself and reducing intensity of the noise signal leaking between the terminals by using a board-to-board connector having ferrite. Patent Document 2 discloses that enhancing isolation of terminals of the board-to-board connector and reducing intensity of the noise signal leaking between the terminals by disposing grounding terminals between the terminals. Still further, it is possible to improve the isolation between the terminals of the board-to-board connector and to reduce the intensity of the control signal leaking into the receiving signal as the noise signal by disposing the terminal for transmitting the control signal and the grounding terminal in zigzag.